Conventionally, for planetary gear reducing mechanisms that are used in geared motors, those wherein all of the gears are structured from spur teeth have been known generally, but there is a tendency for the operating noise of such geared motors to be loud. On the other hand, a geared motor wherein all of the gears are structured helically is known. See, for example, Japanese Unexamined Patent Application Publication No. 2001-173733.
However, when a structure wherein all of the gears are helical is used for planetary gear reducing mechanism for a geared motor, even though the operating noise will be quiet, the gears are difficult to assemble, increasing the amount of labor in assembly. Given this, the present invention is to provide a geared motor wherein the operating noise that is produced by the planetary gear reducing mechanism is reduced, and wherein the increase in the amount of labor in assembly is suppressed because the gear assembly is not difficult.